Strip floating-apparatus

ABSTRACT

A strip-floating apparatus, wherein an inner casing having a jet opening on its end is installed inside an outer casing so as to form a suction opening between the both casings, said jet opening and suction opening are interconnected connected by means of a gas flow passage provided with a recirculating fan, and a cooler is installed this side of said recirculating fan within said gas flow passage.

United States Patent n 1 Eguehi et ai.

[ STRIP FLOATING-APPARATUS [75] Inventors: Isamu Eguchi; Kazuo Akama, both of Aichi-ken, Japan {73] Assignee: Daido Steel Co., Ltd., Ninami-ku,

Nagoya-shi, Aichi-ken, Japan [22] Filed: Apr. 13, 1972 [21] App]. No.: 243,628

[52] U.S. Cl 432/59, 432/8, 266/3, 34/152, 432/21 {51} int. Cl. F27b 9/28 [58} Field of Search 432/59, 8, 21, 4, 432/48, 49, 223; 266/3; 34/18, 152

[56] References Cited UNITED STATES PATENTS 3,198,499 8/1965 Stanley 432/8 [451 July 10, 1973 Z/l941 Keller .1 1266/3 R 5/1959 Stone ct a] 266/3 R Primary Examiner.lohn J. Camby Assistant ExaminerHenry Ct Yuen Attorney-Woodhams, Blanchard & Flynn {5 7 ABSTRACT A strip-floating apparatus, wherein an inner casing having a jet opening on its end is installed inside an outer casing so as to form a suction opening between the both casings, said jet opening and suction opening are interconnected connected by means of a gas flow passage provided with a recirculating fan, and a cooler is installed this side of said recirculating fan within said gas flow passage.

4 Claims, 2 Drawing Figures Patented July 10, 1973 3,744,961

STRIP FLOATING-APPARATUS BACKGROUND OF THE INVENTION l. Field of the invention The present invention relates to an apparatus for use in treating strip materials especially various metallic strips by making them float inside a heat treatment furnace.

2. Description of the prior art It is a well known fact that, as a means of preventing damages on the high-temperature strips in the course of treatment arising from their contact with the conveying roller and so forth inside the furnace, employment of the so-called floating furnace equipped with a floating apparatus has heretofore been popular.

Such a conventional means, however, has been defective in that, when a gas in use for floating the material undergoing the treatment attains too much in temperature, the recirculating fan to supply the gas cannot hold out, and therefore, it is applicable to no more than the furnaces having the internal temperature of 850C at the utmost, that is, such a furnace as for use in heating those materials which require a relatively low temperature for treatment, e.g., copper strip, aluminium strip, etc.

SUMMARY OF THE INVENTION The primary object of the present invention is to provide a strip-floating apparatus which makes up for the defects of the conventional apparatuses and can be applied to heat treatment furnaces having the internal temperature of, for instance, more than 850C.

Another object of the present invention is to provide a strip-floating apparatus which is capable of lowering in advance the temperature of the gas coming in contact with the recirculating fan to such a temperature as will not have any bad influence upon the recirculating fan and renders it possible to apply a commercial recirculating fan to such heat treatment furnaces as having a high temperature for which said fan has hitherto been unsuitable.

A further object of the present invention is to provide a strip-floating apparatus which renders it possible to employ a relatively inexpensive recirculating fan inasmuch as the gas which is supplied by means of the recirculating fan after having its temperature lowered by a cooler can be heated up to such a temperature as will not have any bad influence upon the strip by means of a heating apparatus prior to its being introduced into the furnace and the temperature of the gas to be fed to the recirculating fan can be further lowered by the cooler to thereby minimize the thermal stress to be imparted to the recirculating fan.

A still further object of the present invention is to provide a strip-floating apparatus having the gas flow passage composed of a suction passage and an-exhaust passage adjacent thereto which consists of a material excellent in thermal conductivity and the heat exchanger equipped for the exhaust passage contiguous to a portion of suction passage this side the cooler, which renders it possible to employ a relatively inexpensive recirculating fan as it is so devised that the lowtemperature gas sent from the recirculating fan and passing the exhaust passage is heated to turn into a high-temperature gas through said heat exchanger by virtue of the high-temperature gas passing the suction passage, the resulting high-temperatures gas is jetted from the jet opening to float the strip, the hightemperature gas within the suction passage is cooled by said heat exchanger and, after its being led to the cooler, the temperature at the time of feeding to the recirculating fan can be further lowered, whereby the thermal stress to be imparted to the fan can be minimized.

BRIEF DESCRIPTION OF THE DRAWlNG In the accompanying drawings,

FIG. 1 is a partial front view of vertical section of a furnace equipped with a floating apparatus according to the present invention.

FIG. 2 is a partial birds-eye view taken along the line II-Il in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1, S denotes the strip which is to be moved by means of a driving roller, and plural sets of floating apparatuses 1,1 according to the present invention are installed on the top wall and bottom wall 2, 2' of the furnace so as to face each other by their opening with a slight gap left between the strip and the opening.

The floating apparatus 1 consists of the metallic outer casing 3 whose end forms a contracted opening and a metallic inner casing 4 inserted in said outer casing which is almost similar to the outer casing in shape but is smaller than it and is provided with the blind patch 6 forming the circular jet opening. The ends of the outer casing 3 and inner casing 4 form the circular suction opening 5.

The circular suction opening 5 is connected with the suction passage 8 formed between the lower parts of the inner casing 4 and outer casing 3, and the circular jet opening 7 is connected with the exhaust passage 10 formed in the lower part of the inner casing 4.

The suction passage 8 is equipped with the coller Ill, and the junction of the suction passage 8 and exhaust passage 10 is equipped with the recirculating fan 9 to be driven by the motor 14.

A portion of the exterior of the inner casing 4 constituting the circumference of the exhaust passage 10 is provided with the radiating fins 12 which constitute a heat exchanger, and this portion is equipped with the heating apparatus 13 to which heat is supplied from an external heat-source.

15 denotes the main heating apparatus to heat the strip 8 inside the furnace, and 16 denotes the adiabatic material fixed on the outside of the outer casing 3 as well as the portion contiguous to the cooler 11 of the exhaust passage.

According to the foregoing apparatus, the stream of gas is jetted from the circular jet opening 7 against both sides of the strip S and, by virtue of the static pressure of gas generated in the center of said opening and the dynamic pressure of jet stream, the strip S is held in a floating state, the gas jetted from the jet opening 7 is instantaneously sucked in through the neighboring circular suction opening 5 together with a part of the gas inside the furnace after its striking the strip, and then the sucked gas is cooled by means of the cooler 11, made to flow back to the inner casing 4 and jetted from the circular jet opening 7, whereby the gas for use in floating the strip repeats reflux through the inner casing 4 and the outer casing 3.

Suppose the gas sucked in through the suction opening 5 fails to be cooled by the cooler Ill on this occasion, it will have a temperature equal to that of the gas inside the furnace, and if the temperature of the gas inside the furnace is less than 850C such as in the case of the heating furnace for strips of copper, aluminium and the like, even a commercial recirculating fan may stand a temperature of this much. But, if the temperature of the gas inside the furnace becomes so high as exceeding l,lC such as in the case of the heating furnace for strips of silicon steel, stainless steel and the like, any conventional recirculating fan will never stand it.

According to the present invention, however, inasmuch as the recirculating gas for use in floating the strips is cooled by means of the cooler l 1, any ordinary commercial recirculating fan has proved applicable to even the foregoing heating furnace employing such a high-temperature gas as mentioned above. To give an instance of experiment conducted on the present apparatus, in order to heat a strip of silicon steel up to l,0l0C from 315C, the temperature inside a furnace was elevated to l,060C and a recirculating fan endurable to 770C was installed in this furnace. When the temperature of the gas passing the outlet of the recirculating fan was set to be 750C for safetys sake in the final stage of treating the strip, the temperature of gas at the circular jet opening 7 became 760C, the temperature of gas at a place a little short of the circular suction opening was 800C, and the temperature of gas immediately before its entering the cooler 11 became 790C. The gas was supplied to the recirculating fan after lowering its temperature by 40C to be 750C by means of the cooler 11. It was possible to make the temperature of gas being sucked in the recirculating fan 9 be less than 750C, and there was observed no bad influence of heat upon the recirculating; fan 9. In this context, the strip subjected to treatment was 0.35 mm thick and 762 mm wide, and was moved at the rate of 75 m/minsThe furnace, 54 m long and 1.6 m wide, had its top wall and bottom wall equiped with 31 units of the floating apparatus under the present invention respectively. The number of the recirculating fans employed was five and that of the cooler employed was five.

In the operation of the present apparatus, the gas sucked into the outer casing 3 is supposed to pre-heat the inner casing 4 from the outside; particularly in the region of the heat exchanger 12, the heat exchange is so efficiently effected that not only the sucked gas is cooled but also the jetting exhaust is heated, whereby the object of the present invention can be achieved as intended. Besides, the provision of the heating apparatus 13 within the exhaust passage renders it possible to elevate easily the temperature of the jetting exhaust coming out of the jet opening 7 up to a desired temperature as occasion demands.

The present invention as above is capable of cooling the sucked gas with a cooler prior to its entering the recirculating fan to thereby lower the temperature of said gas to such a degree as is harmless to the recirculating fan. Therefore, it not only is applicable to a hightemperature heating furnace for which any floating apparatus has heretofore been unsuitable but also renders it possible to make the switchover of the conventional heating furnace employing a similar floating apparatus to a heating furnace capable of adopting a further inexpensive recirculating fan.

Although particular preferred embodiments of the present invention have been disclosed hereinabove for the purpose of illustration, it will be understood that variations or modifications thereof which lie within the scope of the invention as defined by the appended claims are fully contemplated.

What is claimed is:

l. A strip-floating apparatus for use in treating strips by supplying a gas which is to flow back inside and outside the furnace by means of a recirculating fan to the jet openings disposed above and below the strip to be treated, which apparatus is characterized by the provision of the suction opening formed around said jet opening, the recirculating fan installed in the gas flow passage connecting the jet opening with the suction opening, and a cooler installed in the gas flow passage for the gas to be sucked into said recirculating fan.

2. A strip-floating apparatus for use in treating strips according to claim 1, wherein a heating apparatus is installed in the gas flow passage for the gas to be blown out of said recirculating fan.

3. A strip-floating apparatus for use in treating strips according to claim 1, wherein said gas flow passage consists of the suction passage connected with the suction opening and equipped with the cooler and the exhaust passage connected with the jet opening, said exhaust passage being composed of a material excellent in thermal conductivity and disposed within said suction passage, and a heat exchanger is installed outside the exchaust passage and so disposed as to come in contact with the high-temperature gas flowing within the suction passage toward said cooler.

4. A strip-floating apparatus for use in treating strips according to claim 3, wherein said exhaust passage is provided with a heat exchanger installed on its outside and a heating apparatus installed on its inside. 

1. A strip-floating apparatus for use in treating strips by supplying a gas - which is to flow back inside and outside the furnace by means of a recirculating fan - to the jet openings disposed above and below the strip to be treated, which apparatus is characterized by the provision of the suction opening formed around said jet opening, the recirculating fan installed in the gas flow passage connecting the jet opening with the suction opening, and a cooler installed in the gas flow passage for the gas to be sucked into said recirculAting fan.
 2. A strip-floating apparatus for use in treating strips according to claim 1, wherein a heating apparatus is installed in the gas flow passage for the gas to be blown out of said recirculating fan.
 3. A strip-floating apparatus for use in treating strips according to claim 1, wherein said gas flow passage consists of the suction passage connected with the suction opening and equipped with the cooler and the exhaust passage connected with the jet opening, said exhaust passage being composed of a material excellent in thermal conductivity and disposed within said suction passage, and a heat exchanger is installed outside the exchaust passage and so disposed as to come in contact with the high-temperature gas flowing within the suction passage toward said cooler.
 4. A strip-floating apparatus for use in treating strips according to claim 3, wherein said exhaust passage is provided with a heat exchanger installed on its outside and a heating apparatus installed on its inside. 